Detonation arrestors are used in flare lines or relief lines where flammable gases are being vented or discharged for burning. The flammable gases that are being flared can sometimes be enriched with oxygen, causing a dangerous condition in which there is potential for an explosion, detonation or other flame front movement in the flare line. Such an event will be referred to as a flame front. The flame front may travel through the flare line towards the source of the flammable gases, which may be a storage tank containing flammable gases.
It is therefore highly desirable to have a device in the flare line that is capable of extinguishing such a flame front as it travels down the flare line. The device must be designed to extinguish a variety of flame fronts including a continuous burn. At the core of such a device is a part that is known as the quenching medium, and various designs have used different such media. The quenching medium is used to extinguish or in other words quench the flame.
Devices presently on the market that are used as detonation arrestors include a device having a quenching medium made of tightly wound expanded metal (aluminum mesh) made by Westech Industrial Ltd. of Sherwood Park, near Edmonton, Canada. The quenching medium includes a core made from fine expanded metal mesh that is rolled into a cylindrical shape, and has its ends cast in liquid steel. Gas passes through the mesh, and while it is useful for stopping detonations, has difficulty withstanding a continuous burn. In a continuous burn, the flame tends to stabilize on the surface of the cell and the aluminum of the expanded metal mesh tends to melt.
Earlier devices have used crimped metal ribbons as the quenching medium, for example as shown in U.S. Pat. No. 2,068,421, to Long et al. This design fails particularly when there is an air-fuel mixture on either side of the arrestor, since then the flame can pass from one side of the arrestor to the other. In a different art, tank venting, unrelated to flare lines, flame arrestors have been used that have used various types of quenching media, such as pebbles (U.S. Pat. No. 1,755,624), pellets (U.S. Pat. No. 1,328,485) and metal balls (U.S. Pat. No. 1,907,976). Other proposals have used sand and gravel. However, this technology has been considered old technology, and has not been considered adequate for todays requirements.
Other United States patents that describe flame arrestors include U.S. Pat. Nos. 290,559; 2,420,599; 2,810,631; 3,148,962 and 3,238,027.
Further, a satisfactory detonation arrestor for flare lines that is capable of withstanding a continuous burn has not to the knowledge of the inventor been previously made.
The inventor has therefore provided a detonation arrestor for connection to a flare line, the flare line having inflow and outflow ends, comprising:
a cell housing defining an interior cavity in fluid connection with the flare line;
first means attached to the cell housing for securing the detonation arrestor to the outflow end of the flare line;
a first flame front diffusor disposed in the first means in line with the flare line, having a diameter slightly greater than the flare line and spaced from the cell housing;
the cell housing including a particulate quenching medium substantially filling the interior cavity; and
second means attached to the cell housing for securing the detonation arrestor to the inflow end of the flare line.
In further embodiments, the particulate quenching medium includes a plurality of heat absorbing and corrosion resistant balls, particularly stainless steel balls; the cell housing includes a deflector ring disposed around the inner circumference of the cavity in the cell housing and extending into the particulate quenching medium; the cell housing includes a filling pipe for filling the cavity with particulate quenching medium, the deflector ring being located half-way across the entry of the filling pipe into the cavity. In this latter embodiment, the first flame front diffusor may be a steel plate having a diameter greater than the diameter of the outflow line, or may include a particulate quenching medium, which itself is preferably a set of stainless steel balls.
The detonation arrestor may also include a second flame front diffusor disposed in the second means in line with the flare line and spaced from the cell housing.
In a further aspect of a detonation arrestor with stainless steel balls or other similar particulate quenching medium, the stainless steel balls are retained in place by a wire mesh supported by flat bars with their short faces abutting against the wire mesh. Cross-supports supporting the flame front diffusor may then be oriented at right angles to the flat bars for maximum strength.
In a still further embodiment, the detonation arrestor comprises:
a cell housing defining an interior cavity in fluid connection with the flare line;
first means attached to the cell housing for securing the detonation arrestor to the outflow end of the flare line;
the cell housing including a plurality of stainless steel balls substantially filling the interior cavity; and
second means attached to the cell housing for securing the detonation arrestor to the inflow end of the flare line
In this latter embodiment, there may be included a deflector ring disposed around the inner circumference of the cavity in the cell housing and extending into the stainless steel balls, and a filling pipe for filling the cavity with stainless steel balls, the deflector ring being located half-way across the entry of the filling pipe into the cavity.